1. Technical Field
The present invention relates to an apparatus that detects overlapped conveyance in which printing sheets are conveyed in an overlapped manner.
2. Related Art
In recent years, there has been put into practice use of RFID (Radio Frequency Identification) technology, which performs non-contact communication with an IC (Integrated Circuit) tag provided with a communication antenna and an IC chip allowing writing or reading of information. Printing sheets incorporating such IC tag are also known; for example, the information written on the surface of the printing sheet or information of other types is stored in the IC tag.
An apparatus, such as a copier and printer, which forms an image on a printing sheet may include an overlapped conveyance detection apparatus which monitors whether printing sheets are being conveyed one after the other; i.e., whether printing sheets are being conveyed in a non-overlapped manner. The overlapped conveyance detection apparatus transmits ultrasonic waves to a printing sheet so that the printing sheet is vibrated by the ultrasonic waves, and detects overlapped conveyance based on attenuation of the ultrasonic waves in the secondary vibration.
An aerial layer is formed in that part of the printing sheet into which the IC tag is incorporated; thus, the attenuation of the ultrasonic waves is larger in that part, possibly leading to erroneous detection of overlapped conveyance.
An advantage of the present invention is to provide an overlapped conveyance detection apparatus using ultrasonic waves, the apparatus being compatible with a printing sheet incorporating an IC tag.